One hot growth area for thermoplastics in the next few years will be long fiber thermoplastics (LFT) as a metal replacement. They feature continuous fiber filaments running the full length of a plastic pellet, boosting strength, stiffness, and impact resistance over a wide temperature range. Pellet lengths can typically be specified in a 6 to 12 mm range while the fiber length in short fiber pellets is typically less than 1 mm.
One of the major suppliers is specialty compounder RTP Co. of Winona, MN, which uses a pultrusion process to manufacture LFT. In pultrusion, continuous fiber rovings are pulled through a polymer melt in a specialized die. The resulting composite strands are cooled and chopped into pellets. Loading levels are typically in the range of 40 to 50 percent. Glass fiber is the most popular reinforcement for cost reasons, but other materials provide different properties. Aramid fiber is used for wear requirements, while stainless steel fiber provides electrostatic dissipation (ESD) and electromagnetic interference (EMI) shielding properties. Carbon fiber provides additional benefits in flexural modulus while also providing ESD properties, according to RTP, which has an excellent FAQ on LFT.
Among recent news, Celanese Corp. announced the acquisition of the long-fiber reinforced thermoplastics business of FACT GmbH (Future Advanced Composites Technology) of Kaiserslautern, Germany, a business unit of The Ravago Group.
At last June’s National Plastics Exposition in Chicago, several LFT technocgies were on display. PolyOne Corp. launched the OnForce LFT compounds, which are optimized for surface finish, stiffness, and toughness. SABIC Innovative Plastics (LNP) showed its StaMax long-glass PP compounds for automotive applications. Several other companies also supply LFT, which is expected to grow at the rate of more than 20 per cent a year when economic conditions improve. The dominant matrix resins are polypropylene and nylon, although others are also widely used.